With the development of the communication technology, fixed phones and mobile phones are increasingly popular, and have become an indispensable part of people's life and work. Today, information becomes more and more important. People have gradually given up the communication manner of letter, which takes a relatively longer time, and turn to use other manners such as telephone to obtain information and improve relationship quickly and conveniently. While the telephone brings convenience to people, many people feel the annoyance brought by modern civilization into daily life to some extent. For example, it is not hard to imagine how people will response when a raspy telephone ring bursts in a still night. Calls in improper time would affect people's life and work unavoidably, particularly some un-emergent calls, especially harassing calls, would seriously affect people's daily life, both physically and mentally.
For avoiding the above problems, powering off is the simplest way. But if the telephone is powered off, the user could not answer any incoming call, including the call from the relatives and friends, and may miss some emergent calls which are very important for the user. Also, after the telephone is powered off, the user easily forgets to power it on when he needs to answer a call, for example, if the connection line of the fixed phone is pulled out last night, a user easily forgets to connect the line with the fixed phone in the next day, which would affect the user for answering some necessary calls. Therefore, although this method is simple, it is extremely inconvenient for the user.
Now for the mobile communication, a service named secretary system is provided. When the mobile phone number of the called party subscribing this service is dialed, if the called party does not want to be disturbed by the phone call, the secretary system would its prompt the calling party to leave message and inform the called party by short message etc. In this situation, the called party could decide whether to call back according to the message left by the calling party. The called party might not call back for unimportant call and could call back for the important call at convenient time, which ensures that the called party will not be disturbed by the incoming call in a given period. A user needs to pay for this way, and the called party usually could not deal with some emergent affairs in time because the secretary system informs the called party by changing the incoming call from the calling party into short message which may be delayed or even be lost. In addition, under the condition of one-way charge for mobile communication, the payout of the called party would be increased for calling back, therefore this method is also inconvenient for the called party.
To solve the problem of call disturbance, another method is the incoming call filtering. When a user does not want to be disturbed by unimportant calls, the user could inform the communication carrier providing this service to allow connection of the calls from certain calling numbers, and refuse to connect the calls from other calling numbers except for these specified calling numbers. In this manner, the user needs to set the calling number frequently, and if too many calling numbers are set, the connecting time would be prolonged, which is still inconvenient for the user.